Run-Time Settings
Return Home, to RSAP-V3 Wiki Run-Time Settings The analysis settings help to alter the performance of RSAP. The settings can be used to speed up the run time, improve the accuracy or limit the analyses. There are two types of run-time analysis settings in RSAP: Encroachment settings and trajectory selection settings. Changing these values can also be used to perform a "quick and dirty" analysis to gain insight and then changed when a more precise answer is needed. For example, in a first Run of a length RSAPv3 problem the minimum number of trajectories may be set to 5 and the maximum to 10 and run the problem. If a more precise answer is desired, the problem can be re-run with the minimum at 10 and the maximum at 40 Encroachment Settings The Encroachment Settings involve values that determine which Encroachments are modelled, how frequently along the segment they are evaluated and the number of trajectories that are selected. These settings are quite often used since they can make a dramatic improvement in analysis speed. · Min Trajectories at each Encr. Location - The minimum number of trajectories used at each Encroachment location. The default value is 10. · Max Traj at each Encr. Location - The maximum number of trajectories used at each Encroachment location. The default value is 40. · Distance Between Encr Locations - The default Encroachment increment is 4 feet. Four feet is currently the suggested maximum Encroachment increment when Point Hazards are present. Consider increasing this value when the hazards on the roadside or median include only Line Hazards or changes to the roadside cross-section. The Encroachment increment should be no greater than the length of the smallest hazard. · Encroachment direction - The Encroachment directions include primary right, primary left, opposing Scribble50Right and opposing left. Likewise, only the roadside on the Primary Direction may be of interest so the Encroachments could be limited to the primary right Encroachments. Choosing to reduce the Encroachments considered will significantly reduce analysis runtime. Trajectory Selection Settings RSAPv3 searches a trajectory database to identify relevant cases based on similarity to the given road-segment characteristics; that is, the program selects trajectory cases that have characteristics which fall within a specified range of those defined in the current project. The selection methodology involves examining and scoring each individual trajectory case based on a quantitative comparison of the roadway characteristics. The individual scores for each of the four criteria are combined into a single representative composite score for the trajectory case and RSAPv3 selects the trajectories with the highest scores for use in the analysis. RSAPv3 selects only those trajectories that have a composite score of 0.93 or higher or until the minimum number of desired trajectory cases are obtained. Although the accuracy of the analysis is expected to improve as the number of "applicable" trajectories cases increase, the analysis time will also increase. For some road segments there may be a relatively large number of trajectory cases with a composite score higher than 0.93. The user should generally not change these values. · Score Cutoff - This criterion is used to define a cutoff value for each characteristic score. When a trajectory case has a score lower than the "Score Cutoff" value for a given roadside characteristic the score is cut in half in order to sufficiently lower the overall composite score and minimize the chance for the trajectory being selected for the analysis. The default value is set to 0.7 · Weight - This criterion is used to assign a "weight" for each characteristic in calculating the weighted average composite score.